Loading...

Messages

Proposals

Stuck in your homework and missing deadline?

Get Urgent Writing Help In Your Essays, Assignments, Homeworks, Dissertation, Thesis Or Coursework & Achieve A+ Grades.

Privacy Guaranteed - 100% Plagiarism Free Writing - Free Turnitin Report - Professional And Experienced Writers - 24/7 Online Support

Determination of ka for a weak acid lab report

27/10/2020 Client: arwaabdullah Deadline: 3 days

Cailin Winokur

Professor Stage

Chemistry II

March 18, 2018

Lab 6: Determination of Ka for a Weak Acid

Procedure: To begin the experiment, carefully cut the tip of the phenolphthalein pipet and add exactly 2 drops of phenolphthalein solution to the unknown weak acid in the beaker. Then swirl the beaker to completely mix the unknown weak acid and phenolphthalein solution. Remove the cap of the Sodium Hydroxide and fill an empty pipet full of the solution. Add NaOH from the pipet into the beaker containing the 4 mL of unknown weak acid one drop at a time, swirling and observing the solution in the beaker after each drop until the color changes to a pale-pink color for at least 5 seconds. Count and record each drop of NaOH added to the beaker, so that you will know exactly how many drops of NaOH were required to cause the solution to change from clear and colorless to pale-pink in color. Next, carefully pour the solution down the sink drain and use the dish soap, tap water, and paper towels to wash and dry the beaker. Repeat, observe, and record. Next, add exactly 10 drops of NaOH from the pipet into the beaker containing the 4 mL of unknown. Gather a pH indicator strip from the kit and place it into the solution in the beaker so that all 4 indicator squares come into contact with the weak acid. Accurately read the pH indicator, record, and repeat. After finishing the experiment, calculate the percent error based on the results that was gathered throughout the experiment.

Exercise 1:

1. Using the data collected in Data Table 2, create a graph of “Drops of NaOH added” vs “pH” where “drops of NaOH added” is on the x-axis and “pH” is on the y-axis. Upload an image of the graph into Graph 1.

C:\Users\hall\Desktop\chart 1.jpg

2. pH indicator strips work by changing color in the presence of solutions with varied pH values. Thinking about your procedure steps and results in Part 1, why do you think the pH of the unknown weak acid was not determined with pH indicator strips until Part 2?

We use the pH indicator strips to calculate the amount of unknown acid in the receiving flask by measuring the specific amount of base it takes to neutralize the acid. There are two major ways to know when the solution has been fully neutralized. The first uses a pH meter in the beaker by slowly adding base until the pH reads exactly 7 (neutral). The next method uses a specific indicator. An indicator is an acid or base whose conjugate acid or base has a color difference from the original compound. The color changes when the solution contains a 1:1 ratio mixture of the differently colored forms of the indicator. The pH equals the p K a of the indicator at the endpoint of the indicator. Since the pH of the solution is known and the volume of titrate is added, we can then deduce how much base was needed to neutralize the unknown sample.

3. Discuss possible causes of error in the experimental procedure. Why do you think there was a percent of error in the pKa and Ka values of the unknown weak acid, in comparison to the values presented in Table 2?

My results were close with a 5% Ka error. This error could have come from the pH key, which may not have been 100 percent read precisely. Also, incorrect measuring of solutions when preparing the experiment could have resulted in error.

4. Do you think using a pH meter instead of pH indicator strips would have created a larger or smaller percent error? Explain your answer.

A pH meter has to be specifically calibrate correctly, so if this was calibrated incorrectly, it could also result in error, however I think that there would be a less of a percent error because a meter instrument is more accurate than strips and gives an exact numerical measurement.

5. Why was phenolphthalein a good indicator to use for determining the equivalence point between the unknown weak acid and strong base?

Phenolphthalein is a great indicator for determining the equivalence point. Is a suitable indicator for strong acid or a strong base. It is also a good indicator for a weak acid or strong base therefore it works well in this experiment.

Data Table 1: Determination of Equivalence Point

Trial 1

Trail 2

Volume of Unknown weak Acid

4ml

4ml

Total number of Drops required to reach equivalence point

114 required drops

104 required drops

Average Number of Drops

Average: 109

Data Table 2: Titration Curve Values

Drops NaOH added

pH Value Trial 1

pH Value Trail 2

pH Value Average

Half-Equivalent Point

54

54

5.0

Equivalent Point

109

109

0

3

1

1

10

2.5

2.5

2.5

20

3

3

3.25

30

3.5

3.5

4

40

4

4.5

4.25

50

4.5

5

4.75

60

5

5.5

5.5

70

6

6

6

80

6.5

6.5

6.5

90

7

7.25

7.5

100

7.5

7.5

7.75

110

8

8

8

120

11

11.5

12

Panel 1: Equivalent Point Number of Drops

The Equivalent Point= 93 Drops

Panel 2: Half- Equivalent Point Number of Drops

The Half- equivalent point= 46 Drops

Data Table 3: Determination of Unknown

pKa of Unknown Weak acid

5.0

Ka of Unknown Weak Acid

.00001

Unkown Weak Acid Identity

Acetic Acid

% Error pka

-44%

% error Ka

5%

C:\Users\hall\Desktop\4.jpg C:\Users\hall\Desktop\3.jpg C:\Users\hall\Desktop\pic 1.jpg C:\Users\hall\Desktop\3.jpg

Conclusion:

This lab demonstrated how a titration can be used to measure the concentration of an weak or strong acid or base in solution. This experiment allowed me to practice how to calculate the molar mass of an unknown acid or base, and determine the equilibrium constant of a weak acid (Ka) or weak base (Kb). By adding NaOH, a strong base, in small increments, it was possible to determine the equivalence point of NaOH and the unknown weak acid. Then, the pH at equilibrium was used in order to find the concentration of the unknown acid at equilibrium. In addition, by using the mass of the unknown weak acid and its concentration at equilibrium, the molar mass of the acid was determined. Finally, by using the equation pKa = -log(Ka) and the half equivalence point pKa, the value of Ka for the unknown weak acid was found.. Even though, I had a 5% error, I still believe I conducted this experiment to the best of my ability. I really enjoyed this lab and would recommend people to try it.

Homework is Completed By:

Writer Writer Name Amount Client Comments & Rating
Instant Homework Helper

ONLINE

Instant Homework Helper

$36

She helped me in last minute in a very reasonable price. She is a lifesaver, I got A+ grade in my homework, I will surely hire her again for my next assignments, Thumbs Up!

Guarantee Your Academic Success!

Hire Professional Writers And Get Best Homework Writing Services In Any Subject

6 writers have sent their proposals to do this homework:

Essay Writing Help
University Coursework Help
Online Assignment Help
Buy Coursework Help
Quality Homework Helper
Top Writing Guru
Writer Writer Name Offer Chat
Essay Writing Help

ONLINE

Essay Writing Help

I am a qualified and experienced Writer, Researcher, Tutor, analyst and Consultant. I hold MBA (Strategic Management) (Finance and Marketing) & CPA.K (Accounting and Finance.)

$62 Chat With Writer
University Coursework Help

ONLINE

University Coursework Help

Hi dear, I am ready to do your homework in a reasonable price.

$62 Chat With Writer
Online Assignment Help

ONLINE

Online Assignment Help

Hi dear, I am ready to do your homework in a reasonable price.

$55 Chat With Writer
Buy Coursework Help

ONLINE

Buy Coursework Help

Hi dear, I am ready to do your homework in a reasonable price.

$62 Chat With Writer
Quality Homework Helper

ONLINE

Quality Homework Helper

Hi dear, I am ready to do your homework in a reasonable price.

$62 Chat With Writer
Top Writing Guru

ONLINE

Top Writing Guru

I am an Academic writer with 10 years of experience. As an Academic writer, my aim is to generate unique content without Plagiarism as per the client’s requirements.

$60 Chat With Writer

Let our expert academic writers to help you in achieving a+ grades in your homework, assignment, quiz or exam.

Similar Homework Questions

Your in Communication - Profit volume ratio in break even analysis - PSYC Life Span Development Psychology - Discoverer of dynamite crossword - Abc3 shaun the sheep game - Stone rolling son of aeolus - Msc computer science sheffield - Reading Instructional Strategies - Kansas city preventative patrol experiment - Research paper - Atlas copco element outlet temperature high - BUSI510 Week 2 Discussion - Is a curriculum map a permanent document - Unit 7 business law assignment - Read and respond-3 - Vcaa psychology past exams - To kill a mockingbird part 1 quotes - James madison research paper - Historical case study psych 630 - Table - Ti-nspire calculus cheat sheet - How does excel calculate error bars - Wiat iii sample report - Honeywell mifare card reader - Theoretical framework - Starbucks customer satisfaction case study - Reasons why students should not use cellphones in school - Unilever in brazil case study solution - Model for writers 12th edition pdf - Managerial Accounting Discussion - Zoot suit characters - Alicia está de buen humor cuando contesta el teléfono. - Sentinel lymph node biopsy icd 10 pcs - Book publishing contract template - Information technology and organizational learning - Gopro case study marketing - The glass menagerie test questions - The Challenge: Communication, Criticism and Discipline, Leadership, Motivation, Rules and Policies - Chase sapphire creating a millennial cult brand - Discussion questions for the matrix answers - Monash medical centre ultrasound - Exercise 6 8 bank reconciliation and adjusting entries lo p3 - Systems Thinking in Advanced Nursing Practice - Week 8 Learning Journal - Niceic pocket guide 14 - Percy jackson chapter summaries - How did federal housing policies institutionalize segregation and wealth disparities? - Healthcare Administration Issues - I want a wife judy brady text - Cdcs training in chennai - Bris cath ed jobs - Modulo art pattern square grid - How to write a ballad poem - Can you capitalize consulting fees - Sgt 300 gas turbine - Multiples and factors poster - Alka seltzer tablet alternative for lava lamp - I need 2000 words content written in website - Sports suitable for mesomorph - Examples of informative language function - N492 Assignment Mod 5: - Greenwood unity cv2gip installation - Kai edo is a licensed public accountant - The witching hour roald dahl - If by rudyard kipling pdf answers - Project scope management presentation - Mystic monk coffee case study solution pdf - Homework assignment 5 - Models of career development ppt - Este teléfono celular tiene quizlet - New earth mining case study solution - How to read novels like a professor chapter 1 - Library business continuity plan - Annotated in cyber - Project management at six flags new jersey - Nova absolute zero worksheet answers - Is bruce almighty a christian movie - Discussion Question:Leadership theories - Save the last dance for me michael buble instrumental - Why do cows have so many nipples - Drama script on animals - Information Systems - Npn small signal model - Hamer v sidway analysis - Global assessment of functioning - Bruker vertex 70 price - Corporate services manager position description - How many square meters in a square mile - Disney values and mission statement - Ogden publications magazines - Legal Ethical - Cash flow from operating activities indirect method example - Review Writing Assignment Peer Review - Follow up discussion provide information or clarification - Account classification method - What should the strategy of edward marshall boehm be - How to calculate euac in excel - Rubric for evaluating children's books - DB 6 - Sfd and bmd for fixed beam